Fix #105450: Resolve box selection issue in Metal

Occlusion query buffers not being cleared to zero resulted in
erroneoues selection in certain situations.

Authored by Apple: Michael Parkin-White

Pull Request: https://projects.blender.org/blender/blender/pulls/107135

source/blender/gpu/metal/mtl_query.mm

@@ -33,6 +33,11 @@ void MTLQueryPool::allocate()
   gpu::MTLBuffer *buffer = MTLContext::get_global_memory_manager()->allocate(buffer_size_in_bytes,
                                                                              true);
   BLI_assert(buffer);
+
+  /* We must zero-initialize the query buffer as visibility queries with no draws between
+   * begin and end will not write any result to the buffer. */
+  memset(buffer->get_host_ptr(), 0, buffer_size_in_bytes);
+  buffer->flush();
   buffer_.append(buffer);
 }